Controlling device



f Dec. 30, 1941. E, E. TEACH l 2,267,959

' CQNTROLLING DEvIE Filed Dec'. '115, 1940 W I I y,11 17 4.9 .95 vf Hls AT-roRNEY- Patented Dec. 30, 1941 2,267,959 CGNTROLLING DEVICE Edwin Everett Teach, Painted Post, N. Y., assignor to Ingersoll-Rand Company, New York, N. Y., a corporation of New Jersey Application December 13, 1940, Serial No. 370,012

8 Claims.

This invention relates to a controlling device and, more particularly, it relates to a device for controlling the operation of a fluid compressor.

In the operation of an electric motor driven luid compressor it is usually desirable, when the receiver pressure exceeds a predetermined pressure value, to stop the compression of further fluid by shutting oi the supply of fluid to the compressor (commonly termed unloading). It is also customary upon unloading the compressor to stop the operation of the motor. However, if the load on the compressor is such that the pressure in the receiver falls rapidly after the compressor has been unloaded it is necessary to recommence the supply of uid to the compressor (commonly termed reloading) in order that more fluid may be compressed. Under such conditions the compressor will reload shortly thereafter and the electric motor will again be started. This form of operation leads to unsatisfactory results since the motor is compelled to start and stop at short intervals which, in time, impairs the eiciency of the motor.

Accordingly, it is an object of this invention to provide a controlling device for an electric motor driven compressor which will allow the motor to operate a predetermined time after the compressor is unloaded.

Another object is to provide a controlling device which will stop the operation of the electric motor a predetermined time after the compressor is unloaded.

A still further object is to provide a controlling device for an electric motor driven compressor' which will permit unloading and reloading of the compressor within a predetermined time While the motor is operating.

These and further objects will be apparent from the following description and drawing in which like numerals refer to the same parts.

Figure l is a plan View of an electric motor driven fluid compressor provided with a controlling device constructed in accordance with the principles of the present invention.

Figure 2 is a sectional View of the controlling device shown in Figure 1, and

Figure 3 is a view taken along line 3 3 of Figure '2.

The fluid compressor l, shown in Fig. 1, is driven by an electric motor 3 through the belt 5. The compressor is provided with an intake unloader 1 and a controlling device 9. Fluid is supplied to the compressor cylinders and |3 through the intake unloader 1 and the pipes |5. The uid compressed by the compressor is discharged through the pipe |1 to the receiver I9.

Electric power for energizing the motor 3 is supplied by the main lines 2|, 23 and 25 through wires 21, 29 and 3| respectively. In the wires 21, 29 and 3|, leading to the motor, is a manually operated switch 33 and a second switch 35 magnetically operated and commonly termed a magnetic starter switch. course, be opened or closed at will by the operator while the switch 35 is controlled by a control circuit connected thereto. This control circuit consists of a wire 31, a starter interlock 39, wire 4|, having a manually operated switch 42 therein for opening the` circuit, a pressure operated switch 43, wire 45, solenoid 41, wire 49, overload relay 5| and wire 53.

The circuit is connected to the wire 3| atterminal by wire 31 and to the wire 29 at terminal 51 by wire 53. Thus, ifswitch 33 is closed., current may then ow through the circuit, assuming that the pressure switch 43 is closed. When current flows through the circuit the solenoid 41 will be energized. Energization of the solenoid will move the rod 59 toward the left to close switch 35. This will start the motor and it will continuato operate; until-the circuit is opened which causes deenergization of the solenoid with the result that the rod 59 is moved toward the right.

The intake unloader 1', as shown in Fig. 2, consists of a casing 6| provided with an opening 63 at one side thereof which is closed by a cover 65. A pair of walls 61 formed integral with the casing 6| extend'within the casing chamber 59 to form a guide for the cylindrical valve 1| having ribs 13. A second opening 15, opposite the opening 63, is formed in the casing 6| and into which the control device casing 11 extends.

The wall of the casing 11 extending into the opening 15 provides a seat 19 for the valve 1|. A spring 8| extending through opening B3' and resting on the cover 65- of the valve 1| normally maintains valve 1| against the seat 19'. In thisposition fluid may 110W by the valve 1I to the compressor inlet'. A second spring 83 also extends through the opening 63 and bears o'n an adjusting rod threadedly engaging the cover 65. The position of this rod may be altered at' will to change the spring tension and is securely locked, in any desired position by the lock nut 8-1. This second spring serves as acushioning device' for the valve 1| when the valve is moved to its closed position. In the closed position of the valve the ribs 13 are aligned with the wallsA 61150' prevent the flow of fluidi to the pipes y|5` ofthe The switch 33 may, of

compressor. In this position the compressor is said to be unloaded. Whereas, when the valve 1| is in the position shown in Fig. 2, the compressor is said to be loaded.

The control device casing 11 is secured to the casing 6| by the bolts 89 which also serve to clamp the cover 9| to the casing 11. In the central portion of the casing 11 is a piston chamber 93 in which a piston 95, bearing against a projection 91 formed on the valve 1 I, is adapted to reciprocate. Obviously, movement of the piston 95 toward the left will move the valve 1I toward the left to unload the compressor. The spring 8|, on the other hand, will move the valve 1| and the piston 95 toward the right when the compressor is reloaded.

The cover 9| has a central opening 99 of slightly smaller diameter than the piston chamber 93 and communicates therewith. By making the opening 99 of smaller diameter the wall of the cover 9| can serve as a stop for rightward movement of the piston. This opening permits communication between the chamber formed in the cover 9| and the piston chamber 93. This chamber is designed to receive fluid under pressure from'the receiver tank |9 of the" compressor upon a predetermined pressure in order that thepiston may be moved by the uid pressure toward the left to unload the compressor.

In order that Ithis may be accomplished, it will be noted that the conduit |03 connects the receiver I9 with' the valve |05. This valve consists of a body |01 having a valve seat |09 and a valve I I. The bore I I3 in the valve body |01 is threaded at its outer end to receive a bushing l5 which serves Ito close the bore and provide a second valve seat ||1 against which the valve surface I|9 may seat. The passage |2| in bushing |I5 is likewise threaded at its outer end in order to receive a second bushing |23. Through the bore |24 of the bushing |23, the passage |2I and the bore ||3 extends a plunger |25 provided at its inner end with a head |21 which bears on the bottom surface of a recess |29 formed in the valve to normally urge the valve III against the seat |09. It should be noted that th'e bore |24 is Vof greater diameter than the diameter of the plunger |25. A spring |3| bears on the valve head |21 and on the bushing |23the tension of which is adjustableA by means of the hand nut resistance of the spring |3I, it will be apparentr that the valve I will beraised from its seat |09 and held against its sealt ||1,

duit |03, into inlet chamber |39, past the valve seat |09, through the bore |35 and conduit |31 to a passage |4| provided in the cover 9|. If, now, the pressure should decrease suiciently to enable the -spring I3| to move the valve against its seat |09, the flow of fluid through the valve body would cease. `Any pressure fluid remaining in the controlling device and conduit 31 may then escape into the bore ||3, of the valve body |01, ow by the seat I1 into the passage |2|, through th'e portion of the bore |24,

which is, not filled by the plunger |25, and thence This will allow fluid to ow from the receiver through the con-l to atmosphere through passages provided in the hand nut |33.

Communication between the passage |4| and the chamber |0| in cover 9| may be through either the orifice |43, provided in the wall between the passage and chamber, or through the port |45 also provided in the common wall. The passage |4| is enlarged at its upper end and is provided with a seat |41 for the ball ch'eck valve |49. The ball check valve |49 is pressed on its seat by a spring |5| which is compressed by the screw plug |53 threadedly engaging the enlarged portion of the passage |4I. This .ball check valve is located below the port |45 and, consequently, it is necessary for the ball check valve |49 to be raised from its seat before uid can flow through the port |45. Fluid supplied on the receiver when the valve rises from its seat |91 will have sufcient pressure to raise the check valve from its seat and fluid may then ow into the chamber |0| through the bore |45. When fluid enters the chamber |0| it will act on th'e piston 95 to move the valve 1| to its unloading position.

Formed by the controlling device casing 11 and the cover 9| is an annular chamber |53 which surrounds and is separated from the piston chamber 93. In the inner wall |55 of the casing 11 is a recess |51 having a valve seat |59 adjacent the port |6| opening into the annular chamber |53.A Communication between the port IGI and the recess |51 is controlled by th'e ball check valve |63, which is held against the seat |59 by the spring |65, retained in the recess |51 by the cover 9|. The recess |51 also communicaites with the chamber |0| in the cover 9| through the port |61. Communication between the recess |51 and the annular chamber |53 may also be had through the capillary tubing |69 which is secured in an appropriate bore |1| opening into the recess |51 in the wall |55.

When fluid under pressure has been supplied to the chamber |0| the uid may pass through the port |61 into the recess |51 and since the 'r pressure in the recess |51 is greater than the Since this tubing restricts the flow of uid there will be a predetermined time delay -before the pressure in the annular chamber |53 is equal to theA pressure in the chamber IUI. The length of time involved will depend upon the length of tubing employed andthe diameter of the bore of the tubing. Obviously, an orice or'other metering device could be employed.l

The annular chamber |53 is connected by the tubing |13, threadedly secured to the outer wall of the casing 11 and opening through a port |15 into the annular chamber, with the pressure ac'tuatedswitch 43. The pressure switch 43 need not be particularly described since it is of the common commercial type which will break the circuit between the terminals |19 and |8| upon being subjected to a predetermined pressure and thus opening the electric circuit controlling the solenoid.

Assuming that th'e receiver pressure reaches a` value which'is sufficient to open the valve |09, fluid under pressure is then supplied to the chamber |0| through port |45 and the orifice |43. The

fluid pressure in chamber |0| will move the pis-` A|69 to the annular chamber |53.

As has been previouslyexplained, there will be a certain time delay before thepres'sure in chamber |53 is equal to the pressure in chamber v|Il| tothe tubing |13.` As a result, the pressure acting on the pressure actuated switch' 43, will be insufcient to operate this switch to open the circuit untilthe pressures in the chambers have been equalized after -thepredetermined time delay. When thisr occurs, vthe circuit is broken and the motor ceases to operate. The motor and compressor thus cease operating and do not resume operation until the pressure'in the receiver tank falls to a point `where the pressure exerted by spring I3| is greater than the pressure in the receiver tank. At this time the spring .ISI acting on 'valve III will return it to its seat |89.

Upon closing of valve I I, the valve bore I I3 is vented to the atmosphere as was previously explained. As the pressure in this bore is reduced,

the pressure of the uid in passage |I|| is reduced and the fluid in the piston chamber 93 and the annular chamber I 53, being at a higher pressure, will begin to escape to the passage I 4| and the bore I I3. In order to prevent rapid reloading of the compressor, as would occur if the pressure acting on the piston was" suddenly reduced, thev flow of fluid from the chamber IIlI is restricted by the orifice |43. This orifice provides the only path of escape for the fluid from chamber IUI, since the pressure in that chamber acts with spring |5| on the ball check |49 to hold it on its seat thus preventing the escape of fluid through the port |45 into the passage 14|.

The port I 6| is provided in order that the pressure in the annular chamber |53 may be reduced more rapidly than would be possible if only the capillary tubing |69 were employed. With this arrangement the pressure in the annular chamber |53 is greater than the pressure in chamber I 0| and, consequently, the ball check valve |63 will open against the pressure of the spring |55. Thus uidmay escape both through the capillary tubing |69 and the port ISI to the recess |51 and thence through port |61 to the chamber |0I.

With a reduction of pressure in the annular chamber |53 and the tubing |13, thepressure acting on the pressure actuated switch 43 will decrease sufliciently to permit the switch to close and the motor control circuit will again be closed thus starting the motor. The switch 43 is so regulated that it will close before the compressor has been reloaded so that the motor may attain full operating speed before the valve 1I has completely opened to reload the compressor. In the event that the load on the compressor is sufficient to cause unloading of the compressor by closing of valve 1I and is capable of reducing the receiver pressure in less time than it takes to equalize the pressure in chambers I 0| and 53, it is obvious that the pressure actuated switch will not open and the motor will continue to operate. When this occurs, the compressor may be unloaded and reloaded while the motor continues to operate at all times, thus increasing the eiiciency and economy of operation of the compressor.

I claim:

1. A controlling device adapted for use with a uid compressor comprising a body, an annular chamber in the body, a discharge conduit for the annular chamber, a cap on the body, en inlet chambenin the cap, av supply conduittosupply compressor discharge fluid to inletv chamber, and

a capillary tube to conveyy fluid from the inletv chamber to the annular chamber restricting. the fluid flow and provide a predetermined time deequals the pressure in thefinlet chamber;

2. The combination with a fluid compressor having anY unloading mechanismand a motor vfor driving the compressor controlled by a pressure actuated device of a body having a piston chamber, a piston in the chamber toactuateftheunloading mechanism,A means to subject" thepiston to compressordischarge pressureV at apre'determined compressor discharge pressure to actuat the unloading mechanism to unload the-compressor, a second chamber in the body, means to introduce compressor discharge vfluid from the rst means to the second chamber at said prede# termined compressor discharge pressure at a predetermined rate, means connecting theise'cl ond chamber to the pressure actuated device whereby the pressure actuatedfdevice is not actuated until after the compressor has ybeen un'- loaded.

3. The combination with a fluid compressor having an unloading mechanism and a motor for driving the compressor controlled by a pressure actuated device, of a body having a chamber therein to receive compressor discharge pressure fluid upon a predetermined compressor discharge fluid pressure, a piston chamber in the body communicating with the first said chamber, a piston in the piston chamber to actuate the unloading mechanism to unload the compressor in response to the compressor discharge fluid pressure, a second chamber in the body, means to delay the iiow of uid from the first said chamber to the n second chamber at a predetermined time, 'and means to connect the pressure actuated device to the second chamber to delay the actuation thereof to a predetermined time after the compressor is unloaded.

4. The combination with a fluid compressor having an unloading mechanism and a motor for driving the compressor controlled by a pressure actuated device, of a body having a chamber therein to receive compressor discharge pressure fluid upon a predetermined compressor discharge fluid pressure, means in the body associated with the chamber responsive to the compressor discharge fluid pressure to actuate the unloading mechanism to unload the compressor, a second chamber in the body in communication with the pressure actuated device, and means between the second chamber and said chamber to delay the flow of compressor fluid to the second chamber and delay actuation of the pressure actuated device to a predetermined time after unloading of the compressor.

5. The combination with a fluid compressor having an unloading valve to control the supply of fluid to the compressor, a receiver into which the compressor discharges, a motor for driving the compressor, and fluid pressure responsive controlling means to start the motor when subjected to a predetermined fluid pressure and to stop the motor when subjected to a predetermined high pressure, of means to supply uid under pressure to said controlling means and said unloader valve at different respective rates to delay operation of said controlling means to stop the motor 6. The combination with a fluid compressor having a pressure vfluid operated unloading valve to control the supply of fluid to the compressor, a receiver into which the compressor discharges, a motor for driving the compressor, and fluid pressure responsive controlling means to start the motor when subjected to a predetermined iiuid pressure and to stop the motor when subjected to a lpredetermined high pressure, of means to supply fluid under pressure to said controlling means and said unloader valve at different respective rates to delay operation of said controlling means to stop the motor and means to equalize thepressures acting on said controlling means and said unloader to delay release of said unloaderY until operation of said controlling means to start the motor. Y

. V'7.- The combination with a fluid compressor having a pressure iiuid operated unloading valve to control Vthe supply of fluid to the compressor, a receiver into which the compressor discharges, a motor for driving the compressor, and fluid pressure responsive controlling means to start the motor when subjected to a predetermined fluid pressure and to stop the motor when subjected to a predetermined high pressure, of a chamber associated with said unloader and a. second chamber associated With said controlling means and having a restricted passage to said first chamber, means to introduce fluid into the first chamber with substantially no obstruction and to restrict the discharge of such fluid therefrom, and means to permit discharge of fluid from the second said chamber to the first said chamber with substantially no restriction.

8. The combination with a Afluid compressor having a. pressure fluid operated unloading valve to control the supply of fluid to the compressor, a receiver into which the compressor discharges, a motor for driving the compressor, and fluid pressure responsive controlling means to start the motor when subjected to a predeterminedv EDWIN EVERE'I'I TEACH. 

